[seqfan] Re: N = 3417. Now replace a digit by the "multiply" sign

[Neil Sloane]

Eric, That sequence is worth including in the OEIS - can you submit it?
(If you already did, could you post the A-number here?)
Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com



On Tue, Aug 27, 2019 at 4:12 PM Robert Israel <israel at math.ubc.ca> wrote:

> I meant 10*n, not concatenation.
>
>
> Sent from my Samsung Galaxy smartphone.
>
>
> -------- Original message --------
> From: David Seal <david.j.seal at gwynmop.com>
> Date:2019-08-27  2:03 PM  (GMT-05:00)
> To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> Cc:
> Subject: [seqfan] Re: N = 3417. Now replace a digit by the "multiply" sign
>
> No, at least if I've understood the definition correctly:
>
> 101 is a hit because 1*1 = 1 divides it.
>
> 10101 is not a hit because neither 1*101 = 101 nor 101*1 = 101 divides it.
> (Nor does 10*01 = 10. The definition doesn't seem to allow that erasure,
> but it means that my answer of "No" is not affected if I've misunderstood
> that point.)
>
> David
>
>
> > On 27 August 2019 at 17:30 Robert Israel <israel at math.ubc.ca> wrote:
> >
> >
> > Is it not true that 10 n is a hit whenever n is?
> >
> > Sent from my Samsung Galaxy smartphone.
> >
> >
> > -------- Original message --------
> > From: Éric Angelini <bk263401 at skynet.be>
> > Date:2019-08-27  10:57 AM  (GMT-05:00)
> > To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> > Cc:
> > Subject: [seqfan] N = 3417. Now replace a digit by the "multiply" sign
> >
> > Hello SeqFans,
> >
> > Take an integer N (for example N = 3417).
> > Erase one of N's digits to form integers P and Q.
> > (For N = 3417, erasing 4 produces P = 3 and Q = 17).
> > If P*Q divides N, we have a hit.
> > (this is the case here as 3*17 = 51 and 3417/51 = 67
> > although the other possible erasure doesn't produce
> > an integer: 34*7 = 238 and 3417/238 = 14.35714...)
> >
> > Jean-Marc Falcoz has computed 10,000 such « hits »
> > (with N > 99 and Q that cannot have a leading 0,
> > except if Q = 0); he noticed that the density of
> > hits decreases dramatically when N gets bigger and
> > bigger. Which leads to this: is the hit-sequence
> > finite? More pictures and data here, for those
> > who might be interested:
> > https://bit.ly/2Lag2Fh (in French).
> > Best,
> > É.
> >
> > --
> > Seqfan Mailing list - http://list.seqfan.eu/
> >
> >
> > --
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